Telit Wireless Solutions GE863-QUAD - Manual (Page 52)

GE863-QUAD
GE863-PY
1vv0300715 Rev. 1 - 19/09/06
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved page 52 of 79
9 SIM DESIGN GUIDES
In all Telit modules there are five pins for SIM card holder connection
These lines are:
SIMVCC (SIM Power supply)
SIMRST (SIM Reset)
SIMIO (SIM Data)
SIMIN (SIM Presence/Absence)
SIMCLK (SIM Clock)
SIM connection must take in account of four key issues:
9.1 Data Integrity
Standard rules for digital layout and routing must be followed taking in consideration that SIMCLK has
frequency of 3.57 MHz and SIMIO has 9600Bps baud rate.
9.2 EMI/EMC
This is a key aspect to consider designing an application based on TELIT module with internal
antenna and/or without a proper-shielded box. Some of these conditions may occur:
- Antenna picks-up digital noise coming from SIM card lines.
- Antenna radiated field may interfere digital lines.
- Digital lines (in particular clock) may radiate spurious in the surrounding
space.
To overcome all these potential problems, connection lines must be kept as short as possible and
shielded.
SIM-holder position has to be as far as possible from antenna.
RF bypass capacitors (10pF...33pF) closed to SIM card SIM-holder are another good care.
When connection is not short, insertion of 10..100ohm resistor with 10..33pF capacitor (RC filter) is a
good caution to improve EMI from SIMCLK line.
Do not insert resistor on SIMVCC, SIMRST and SIMIO lines, their use is not supported by SIM
electrical interface.
9.3 ESD
Take standard ESD caution if application based on TELIT module has SIM holder with contacts
reachable from human body.